Arrangements of this kind are used, above all, when testing wheel brakes so that their brake torque may be determined while the vehicle is travelling, rather than on the test stand only. An arrangement of the type in question, useful with motor vehicles of various makes and sizes, is known from the prospectus "Radnaben-Drehmoment-Aufnehmer" by Messrs. Soemer GmbH of D-5940 Lennestadt 11. The measuring hub of that arrangement is a ring which comprises a plurality of chambers located between a flange-like radially inner peripheral area and an outer peripheral area and containing strain gauges. The strain gauges are connected by a slip ring arrangement to a measuring line which can be attached to the body of a test vehicle. The flange-like, radially inner peripheral area of the measuring hub is clamped by a first set of screws between a flange of a vehicle hub and a disc-shaped, first adapter which is centered at its inner periphery on a centering extension formed at the wheel hub and which, in turn, centers the measuring hub by its outer periphery. A second adapter is secured to the face end remote from the vehicle hub of the measuring hub; it includes a centering extension which is aligned with the centering extension of the vehicle hub and has the same diameter as that centering extension. The centering extension of the second adapter centers the wheel body of a vehicle wheel which, instead of being fixed to the flange of the vehicle hub by the tightening of screw bolts, is fastened to the second adapter by a set of wheel bolts.
With this known arrangement, the vehicle wheel is offset axially outwardly, as compared to its normal direct fixing on the wheel hub, by a distance which corresponds to the sum of the thicknesses of the measuring hub and the second adapter and measures 38 mm, in spite of the slender design of these two components. This means that the track of a motor vehicle which has each of its wheels mounted on the vehicle hub through intermission of such a measuring hub, including the adapters is wider by 76 mm than the normal state. Such widening of the track may cause considerable changes in the driving behavior of a motor vehicle. Therefore, any experience gained in braking tests of such a vehicle cannot be readily transferred to identical motor vehicles the wheels of which, however, are fastened directly to the wheel hubs. That applies especially to the front wheels whose roll radius and other geometric data are varied considerably by measuring hubs disposed in the known manner.